In general, a spark plug includes a center electrode and a ground electrode at a front side thereof. The center electrode projects from a front end of an insulator in a state where the center electrode is held in an axial hole of the insulator. Meanwhile, the ground electrode is joined to a front end portion of a metal shell.
As one type of spark plug, a spark plug is present in which a ground electrode tip is joined to a ground electrode. In a general method, in joining the ground electrode tip to the ground electrode, first, a ground electrode member is welded to a metal shell, and then resistance welding (or resistance welding and laser welding) is performed to weld the ground electrode tip to the ground electrode member (See Japanese Patent Application Laid-Open (kokai) No. 2013-206789).